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Boosting acetate production from waste activated sludge (WAS) fermentation is often hindered by the inefficient solubilization in the hydrolysis step and the high hydrogen pressure ( p H 2) during the acidogenesis of C3–C5 short-chain fatty acid (SCFAs), i.e., propionate (HPr), butyrate (HBu) and valerate (HVa). Therefore, this study employed persulfate (PS) oxidation and C3–C5 incomplete-oxidative sulfate reducing bacteria (io-SRB) metabolizers to tailor SCFAs conversion from WAS fermentation. The decomposition efficiency, performance of SCFAs production was investigated. Results showed that the PS significantly promoted WAS decomposition, with a dissolution rate of 39.4%, which is 26.0% higher than the un-treated test. Furthermore, SCFAs yields were increased to 462.7 ± 42 mg COD/g VSS in PS-HBu-SRB, which was 7.4 and 2.2 times higher than that of un-treated and sole PS tests, respectively. In particular, the sum of acetate and HPr reached the peak value of 85%, indicating that HBu-SRB mediation promoted the biotransformation of HBu and macromolecular organics by reducing the p H 2 restriction. Meanwhile, sulfate radical (SO 4 ∙-)-based oxidation (SR-AOPs) was effective in the decomposition of WAS, the oxidative product, i.e., sulfate served the necessary electron acceptor for the metabolism of io-SRB. Further analysis of Mantel test revealed the cluster of the functional genus and their interaction with environmental variables. Additionally, molecular ecological network analysis explored the potential synergistic and competitive relationships between critical genera. Additionally, the potential synergistic and competitive relationships between critical genera was explored by molecular ecological network analysis. This study provides new insights into the integration of SR-AOPs with microbial mediation in accelerating SCFAs production from WAS fermentation. [Display omitted] • Integration of SR-AOPs and io-SRB mediation tailored SCFAs conversion from WAS. • SR-AOPs efficiently promoted WAS decomposition with hydrolysis rate increased by 26%. • HBu-SRB promoted C2–C3 SCFAs conversion by reducing the p H 2 restriction. • Synergetic relationship among io-SRB and fermentative genera was revealed. • Thermodynamic mechanism of acetate-oriented conversion by io-SRB was explored. [ABSTRACT FROM AUTHOR]

Most studies have employed aeration-biofiltration process for the simultaneous removal of iron, manganese and ammonia in groundwater. However, what's inside the 'black box', i.e., the potential contribution of functional microorganisms behavior and interactions have seldom been investigated. Moreover, little attention has been paid to the correlations between environmental variables and functional microorganisms. In this study, the performance of industrial-scale biofilters for the contaminated groundwater treatment was studied. The effluent were all far below the permitted concentration level in the current drinking water standard. Pyrosequencing illustrated that shifts in microbial community structure were observed in the microbial samples from different depths of filter. Microbial networks showed that the microbial community structure in the middle- and deep-layer samples was similar, in which a wide range of manganese-oxidizing bacteria was identified. By contrast, canonical correlation analysis showed that the bacteria capable of ammonia-oxidizing and nitrification was enriched in the upper-layer, i.e., Propionibacterium, Nitrosomonas, Nitrosomonas and Candidatus Nitrotoga. The stable biofilm on the biofilter media, created by certain microorganisms from the groundwater microflora, played a crucial role in the simultaneous removal of the three pollutants. [ABSTRACT FROM AUTHOR]

Current studies have employed various chemicals for disintegrating and hydrolyzing microbial cells in waste activated sludge (WAS). However, a comprehensive process assessment over the whole anaerobic digestion process has seldom been proposed. Besides, the characterization of microbial community responses to these chemicals is not well understood. In this study, the effects of five typical chemicals: solubilizer (β-cyclodextrin, CD), alkaline (NaOH), peroxide (peracetic-acid, PA), biological (rhamnolipid, RL) and chemical (sodium dodecylsulphate, SDS) surfactants on WAS digestion were examined. Higher efficiencies of WAS solubilization, hydrolysis and acidification were achieved by CD treatment, followed by RL and SDS. Methanogenesis was also strongly chemicals-dependent. Shifts in microbial community structure were observed in all chemical-pretreated WAS. The community in RL, CD and PA was dominated by microorganisms that anaerobically hydrolyze organics to acids, while that in NaOH and SDS was mainly associated to biogas production. This study proved that the overall performance of WAS digestion was substantially depended on the initial chemical pretreatments, which in turn influenced and was related to the microbial community structures. Although the economic advantage might not be clear yet, the findings obtained in this work may provide a scientific basis for the potential implementation of chemicals for WAS treatment. [ABSTRACT FROM AUTHOR]

The effects of three widely-used surfactants on waste activated sludge (WAS) fermentation and microbial community structures were investigated. Rhamnolipid bio-surfactants (RL) showed more positive effects on WAS hydrolysis and acidification compared to chemosynthetic surfactants, such as sodium dodecylsulphate (SDS) and sodium dodecyl benzene sulfonate (SDBS). The highest SCOD and VFAs concentrations obtained with RL were 1.15-fold and 1.16-fold that of SDS, and up to 1.73 and 3.63 times higher than those obtained with SDBS. Pyrosequencing analysis showed that an evident reduction in bacterial diversity in surfactant-treated WAS. Moreover, acid-producing bacteria (such as Megasphaera and Oscillibacter ), detected with RL, were (6.8% and 6.4% in proportion) more abundant than with SDS, and were rarely found in SDBS and the control. The results also revealed that RL allowed efficient hydrolysis enhancement and was favorable to functional microorganisms for further acidification during WAS fermentation. [ABSTRACT FROM AUTHOR]

Exploration of value-added products from wastewater treatment plants (WWTPs) was promising for its sustainable development. This study simultaneously addressed the possibility of volatile fatty acids (VFAs) production boost and cellulosic components recovery from fine-sieving fractions (FSF) under initial alkaline conditions. The step utilization of FSF was relatively untapped in similar literatures. The effect of different initial pH values with 8.5, 9.5 and 10.5 (defined as F-8.5, F-9.5 and F-10.5) on fermentation performance were investigated. Then, the fermentation residues were collected to evaluate the changes in chemical structure and thermodynamic properties by fourier transform infrared spectroscopy (FTIR) and thermo-gravimetric (TG) analysis. Furthermore, analysis of the changes in microbial community structure and the interaction between functional genus and performance parameters were undertaken by high throughput sequencing and canonical correspondence analysis (CCA). Results showed that F-10.5 obtained the highest VFAs yields of 234 mg/g VSS, due to efficient polysaccharides release and inhibited methane production. However, high alkaline intensity caused proteins denaturation. Acidogenesis kinetics suggested that the fermentation rate was chemical-dominated. Although crystalline structure was more disordered with increasing alkalinity, the weight loss was lower than 2.5%, making it possible to recover cellulose from fermented residues. Interaction between functional genus and performance parameters revealed the microbial mechanism during the alkaline fermentation. Consequently, the initial-alkaline motivated fermentation was proved to be a promising technology in value-added products recovery to be cost economic, energy positive and environmental friendly. [Display omitted] • VFAs production was accelerated due to efficient chemical-dominated hydrolysis. • Change in cellulose structure was detected with less weight loss after fermentation. • Alkaline fermentation significantly affected the microbial community structure. • The process was evaluated to be cost effective, energy and environmental positive. [ABSTRACT FROM AUTHOR]

Maximizing the internal carbon sources in raw wastewater was found to be an alternative option to alleviate the financial burden in external carbon sources (ECS) addition to the biological nutrient removal (BNR) process. Based on previous studies on particulate recovery via fine-sieving technologies, alkali pretreatment was used to improve the short-chain fatty acid (SCFA) production from the fine-sieving fractions (FSF). Hydrolysis performance and methane production were monitored to evaluate the reasons for the SCFA boost. Besides, the microbial community structure was evaluated by high-throughput sequencing. Furthermore, mass balance and financial benefits were preliminarily estimated. The results showed that alkali pretreatment effectively promoted the generation of SCFAs with 234 mg/g volatile suspended solids (VSS), almost double that of the control test. This was partially attributed to the efficient hydrolysis, with soluble polysaccharides and protein increased by 2.1 and 1.2 times compared to that of the control, respectively. Inhibition of methanogens was also devoted to the accumulation of SCFAs, with no methane production until 150 h at high pH value. Finally, a preliminary evaluation revealed that 44.51 kg/d SCFAs could be supplied as the electron donor for denitrification, significantly reducing the cost in ECS addition for most wastewater treatment plants (WWTPs) with carbon insufficiency. [ABSTRACT FROM AUTHOR]

Graphical Abstract Highlights • First investigated the high COD/NO 3 −-N ratio of indole wastewater in mixed culture. • Through nitrate to observe the denitrification and methanogenesis co-existence. • Nitrate was found to facilitate indole degradation and inhibit methane formation. • The metabolites were identified based on 13C-indole isotope analysis. • A dynamic community analysis was presented to study the microbial structures. Abstract Batch experiments were conducted to investigate the effect of nitrate on indole degradation characteristics and methanogenesis under mixed denitrification and methanogenesis culture for the first time. The degradation characteristics were studied under various nitrate concentrations. Nitrate was found to facilitate indole degradation and inhibit methane formation, and the optimum concentration was 50 mg L−1 (COD/NO 3 −-N = 12). Balance analyses showed that nitrate mainly affected indole-C, which generated a higher degree of indole mineralization under NO 3 −-N treatment than in the control. Furthermore, GC–MS combined with 13C-isotope analyses conclusively identified the intermediate metabolites, which included the hydroxylated compounds oxindole and isatin, and the methylated compound 3-methylindole. The results indicated that oxindole did not accumulate and was quickly reduced when nitrate was added, but 3-methylinole, as a recalcitrant material, accumulated without reduction. High-throughput sequencing technology was used to analyse the dynamic microbial community. Results showed that the denitrifying bacterial genera Acinetobacter , Candidimonas and Longilinea accumulated in denitrification stage and decreased in methanogenesis stage, whereas the fermentation genera Alcaligenes and Thermogutta increased in methanogenesis stage. The genera Methanosphaerula and Methanothrix constituted the dominant archaeal communities. The findings obtained in this work may provide a theoretical basis for treatment with N-heterocyclic compounds under mixed culture. [ABSTRACT FROM AUTHOR]

Sulfadiazine (SDZ) is widely used in clinical treatment, livestock husbandry and aquaculture as an antibacterial agent, resulting in environmental risks. In this work, batch experiments were conducted to investigate the characteristics of SDZ biodegradation and reaction mechanisms in a nitrate anaerobic denitrifying system for the first time. The results showed that 98.52% of the SDZ, which had an initial concentration of 50 mg L−1, was degraded after 70 h, indicating that the removal efficiency of SDZ in anaerobic denitrifying system was 55.27% higher than that in anaerobic system. Furthermore, LC-MS-MS analysis confirmed that SDZ could be degraded into 16 byproducts via 3 main degradation pathways that contained 6 different reactions. After analyzing the microbial communities of the reactor, the denitrifying bacteria and desulfurizing bacteria Desulforhabdus , Ignavibacterium , SBR1031_norank , Nocardioides , etc. were highly associated with the removal of SDZ in the system. The biological toxicity test of the effluent indicated that the remaining organic matter and inorganic matter of the effluent could provide nutrients for E. coli and promote its growth. In other words, anaerobic denitrifying systems are highly efficient, simple and environmentally friendly, and have an impressive prospect in the biodegradation of sulfonamide antibiotics. Image 1 • Mixed microbes were first cultivated to remove SDZ in anaerobic denitrifying system. • Nitrate system could promote SDZ degradation and eliminate the biotoxicity of SDZ. • 3 metabolic pathways of SDZ that based on 6 chemical reactions were speculated. • Denitrification and desulfurization bacteria could promote SDZ degradation together. [ABSTRACT FROM AUTHOR]

• The quinoline wastewater treatment was first investigated in the MEC-AD system. • The performance of quinoline degradation was strengthened at a voltage of 1.0 V. • CH 4 production was increased to 1.5-fold in MEC-AD compared to the AD. • Simultaneous quinoline-C and quinoline-N removal were achieved in MEC-AD. • Exoelectrogens, methanogens, anammox and degradation bacteria have coexisted. In this study, the feasibility of quinoline-wastewater treatment was investigated in a coupled microbial electrolysis cell and anaerobic digestion system (MEC-AD). Improved degradation and enhanced mineralization of quinoline were obtained, and the optimal voltage was determined to be 1.0 V. Effective removal of quinoline at relative high concentration, and a 1.5-fold increase in methane production were achieved. The results indicated that the MEC-AD could simultaneously remove carbon and nitrogen from quinoline. Gas chromatography-mass spectrometry analysis identified 2-hydroxyquinoline and 8-hydroxycoumarin as the intermediates of quinoline. The formation and degradation of metabolites were rapid, and they did not accumulate in the MEC-AD. The results of microbial community structure analysis demonstrated that the functional species were enriched and coexisted, and that the dominant bacterial genera were SM1A02 , Comamonas , Desulfovibrio , Geobacter, and Actinomarinales_norank ; the dominant archaeal genera were Methanocorpusculum and Nitrosoarchaeum. Furthermore, the applied current played a selective role in the enrichment of microorganisms. [ABSTRACT FROM AUTHOR]

To enhance hydrogen recovery from high-solid waste activated sludge (WAS), microbial electrolysis cells (MECs) were used as an efficient device. The effects of WAS concentrations were firstly investigated. Optimal concentration for hydrogen production was 7.6 g VSS/L. Maximum hydrogen yields reached to 4.66 ± 1.90 mg-H 2 /g VSS and 11.42 ± 2.43 mg-H 2 /g VSS for MECs fed with raw WAS (R-WAS) and alkaline-pretreated WAS (A-WAS) respectively, which was much higher than that obtained traditional anaerobic digestion. Moreover, no propionic acid accumulation was achieved at the optimal concentration. Effective sludge reduction was also achieved in MECs feeding with A-WAS. 52.9 ± 1.3% TCOD were removed in A-WAS MECs, meanwhile, protein degradation were 50.4 ± 0.8%. The 454 pyrosequencing analysis of 16S rRNA gene revealed the syntrophic interactions were existed between exoelectrogen Geobacter and fermentative bacteria Petrimonas, which apparently drove the efficient performance of MECs fed with WAS. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment was studied to analyze the influence on waste activated sludge (WAS) reduction, methane production and microbial community structure during anaerobic digestion. Methane production from alkaline pretreated sludge (A-WAS) (pH = 12) increased from 251.2 mL/L d to 362.2 mL/L d with the methane content of 68.7% compared to raw sludge (R-WAS). Sludge reduction had been improved, and volatile suspended solids (VSS) removal rate and protein reduction had increased by ∼10% and ∼35%, respectively. The bacterial and methanogenic communities were analyzed using 454 pyrosequencing and clone libraries of 16S rRNA gene. Remarkable shifts were observed in microbial community structures after alkaline pretreatment, especially for Archaea . The dominant methanogenic population changed from Methanosaeta for R-WAS to Methanosarcina for A-WAS. In addition to the enhancement of solubilization and hydrolysis of anaerobic digestion of WAS, alkaline pretreatment showed significant impacts on the enrichment and syntrophic interactions between microbial communities. [ABSTRACT FROM AUTHOR]